Tempered glass plate and method for producing same

Abstract

The present invention relates to a strengthened glass sheet having a first main surface, a second main surface which faces the first main surface, and an end surface, in which at least one of the first main surface and the second main surface has a surface compressive stress formed by a chemical strengthening treatment, the strengthened glass sheet includes a strengthened portion in which a planar compressive stress is formed along the end surface in a direction parallel with the end surface, the planar compressive stress of the strengthened portion has a maximum value of 1-120 MPa, and the strengthened portion has a width, as measured from the end surface in a direction normal to the end surface, of 0.5 times or more a thickness of the strengthened glass sheet.

1 . A strengthened glass sheet having a first main surface, a second main surface which faces the first main surface, and an end surface,
 wherein at least one of the first main surface and the second main surface has a surface compressive stress formed by a chemical strengthening treatment,   the strengthened glass sheet comprises a strengthened portion in which a planar compressive stress is formed along the end surface in a direction parallel with the end surface,   the planar compressive stress of the strengthened portion has a maximum value of 1-120 MPa, and   the strengthened portion has a width, as measured from the end surface in a direction normal to the end surface, of 0.5 times or more a thickness of the strengthened glass sheet.   
     
     
         2 . The strengthened glass sheet according to  claim 1 , wherein the surface compressive stress has a CS of 200 MPa or more. 
     
     
         3 . The strengthened glass sheet according to  claim 1 , wherein the surface compressive stress has a DOL of 5 μm or more. 
     
     
         4 . The strengthened glass sheet according to  claim 1 , wherein the end surface comprising the strengthened portion has no surface compressive stress formed therein by a chemical strengthening treatment. 
     
     
         5 . The strengthened glass sheet according to  claim 1 , wherein the strengthened portion has no planar tensile stress. 
     
     
         6 . The strengthened glass sheet according to  claim 1 , comprising a protective layer provided to the end surface comprising the strengthened portion. 
     
     
         7 . The strengthened glass sheet according to  claim 1 , comprising, in mole percentage on an oxide basis, 0.003-1.5% Fe 2 O 3 , 56-75% SiO 2 , 0-20% Al 2 O 3 , 8-22% Na 2 O, 0-10% K 2 O, 0-14% MgO, 0-5% ZrO 2 , and 0-12% CaO. 
     
     
         8 . The strengthened glass sheet according to  claim 1 , wherein the strengthened portion has been formed to the end surface in a position located at a distance of 1.0 to 10 times the thickness of the strengthened glass sheet from a corner where the end surface meets an adjoining end surface. 
     
     
         9 . The strengthened glass sheet according to  claim 1 , having a planar tensile stress formed in a direction parallel with the end surface in a position adjacent to the strengthened portion on the opposite side to the end surface. 
     
     
         10 . The strengthened glass sheet according to  claim 1 , having an even specific gravity as a whole. 
     
     
         11 . The strengthened glass sheet according to  claim 1 , wherein the end surface has a chamfer at a boundary between the end surface and the first main surface and at a boundary between the end surface and the second main surface. 
     
     
         12 . A method of producing the strengthened glass sheet according to  claim 1 , the method comprising:
 a chemical strengthening treatment step of immersing at least one of main surfaces of a glass sheet in a molten salt to form a surface compressive stress in the main surface of the glass sheet; and   an end surface strengthening step of, after the chemical strengthening treatment step, forming a planar compressive stress along an end surface of the glass sheet in a direction parallel with the end surface,   wherein in the end surface strengthening step, the glass sheet is heated so that a temperature T 1  is not lower than a strain point of the glass sheet, where the temperature T 1  is a temperature of a portion of the glass sheet lying at a distance equal to a thickness of the strengthened glass sheet from the end surface along a direction normal to the end surface; the end surface has a temperature T 2  which is lower than a softening point of the glass sheet; and a relation T 1 >T 2  is satisfied.   
     
     
         13 . The method of producing a strengthened glass sheet according to  claim 12 , wherein in the end surface strengthening step, the planar compressive stress is formed in the end surface of the glass sheet by irradiation with laser light. 
     
     
         14 . The method of producing a strengthened glass sheet according to  claim 13 , wherein in the end surface strengthening step, the laser light with which the glass sheet is irradiated has such a wavelength that the glass sheet has an absorption coefficient α less than 100 [cm −1 ]. 
     
     
         15 . The method of producing a strengthened glass sheet according to  claim 13 , wherein in the end surface strengthening step, the wavelength of the laser light is 250-5,000 nm. 
     
     
         16 . The method of producing a strengthened glass sheet according to  claim 12 , comprising, after the chemical strengthening treatment step, a cutting step of cutting the glass sheet that has undergone the chemical strengthening treatment. 
     
     
         17 . The method of producing a strengthened glass sheet according to  claim 16 , wherein in the cutting step, the glass sheet is cut by a method in which thermal-stress scribing is used. 
     
     
         18 . The method of producing a strengthened glass sheet according to  claim 12 , wherein a protective layer is formed on the end surface after the end surface strengthening step.